Update shadow visibility logic in ScrollingBottomViewSceneLayer

This patch updates the composited bottom toolbar's shadow visibility
to depend on the android view's visibility. If the android view is
visible, the compositor shadow is not.

Bug: 854642
Change-Id: Ib1f3f1491fc8728ad5f49d8170145bd5d3161ce2
Reviewed-on: https://chromium-review.googlesource.com/1108343Reviewed-by: Pedro Amaral <amaralp@chromium.org>
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569305}

chrome/android/java/src/org/chromium/chrome/browser/compositor/scene_layer/ScrollingBottomViewSceneLayer.java

@@ -5,6 +5,7 @@
 package org.chromium.chrome.browser.compositor.scene_layer;
 
 import android.graphics.RectF;
+import android.view.View;
 
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.chrome.browser.compositor.LayerTitleCache;
@@ -75,8 +76,11 @@ public class ScrollingBottomViewSceneLayer extends SceneOverlayLayer implements
     @Override
     public SceneOverlayLayer getUpdatedSceneOverlayTree(RectF viewport, RectF visibleViewport,
             LayerTitleCache layerTitleCache, ResourceManager resourceManager, float yOffset) {
+        // The composited shadow should be visible if the Android toolbar's isn't.
+        boolean isShadowVisible = mBottomView.getVisibility() != View.VISIBLE;
+
         nativeUpdateScrollingBottomViewLayer(mNativePtr, resourceManager, mResourceId,
-                mTopShadowHeightPx, viewport.height() + mCurrentOffsetPx, mCurrentOffsetPx > 0);
+                mTopShadowHeightPx, viewport.height() + mCurrentOffsetPx, isShadowVisible);
 
         return this;
     }